37
3
3 Elements
3.5 Timer
100 ms 10 ms
1 ms
accumulation-
type
100 ms
accumulation-
type
1ms
T0 to T191
192 points
※1
T192 to T199
8 points ※2
T200 to T245
46 points ※1
T246 to T249
4 points ※3
T250 to T255
6 points ※4
T256 to T511
256 points
※1
• [1] It cannot be retained upon power failure.
• [2] It cannot be retained upon power failure, and is used for subprograms and interrupt subprograms.
• [3] It can be retained upon power failure, and the timing value can be accumulated.
• [4] It can be retained upon power failure, and the timing value can be accumulated.
An unoccupied timer number can be used as a data register for numerical value storage.
The timer accumulates the clock pulses of 1 ms, 10 ms, 100 ms, and so on in the PLC. When the timing value
reaches the preset value, the contacts take action only during execution of the coil instruction or END instruction.
You can use the constant (K) of the program memory as the preset value, or use the content of the data register (D)
to specify the preset value.
• The content of D must be set before timing starts. After timing starts, changes to the data of D can only take effect
when timing starts next time.
The following describes the possible timing length from timer coil driving to timer contact action:
● The longest timing length is (T + T0 + a), wherein T is the preset timing value, T0 is project scanning
time, and a is the timing step of the timer.
● The shortest timing length is (T – a).
● When the timer contact instruction is before the coil instruction, the timing length is (T + 2T0), which is
the least ideal condition.
● The b contact of the timer can be used for delay-disconnected and self-oscillating output signals.
● The PLC also provides special timer instructions, for example, TTMR, and STMR. For details, see the
descriptions on these instructions.
Example 1: The general timer T200 has a step of 10 ms, and the actual action delay is 150 × 10 ms ＝ 1500 ms
(1.50s). The action principle is as follows:
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